为什么我的函数只返回[3,2,].它应该打印出元素1吗？
function reverseArr(arr) {
var reverse = [];
for (var i = 0; i < arr.length; i++)
reverse.push(arr.pop());
return reverse;
}
console.log(reverseArr([1, 2, 3]));
我试图了解如何从输入文件中读取信息并将该数据写入输出文件。我了解如何从文件中读取并显示其内容，但我不了解如何写入文件或显示其内容。我的程序运行良好，但是当我检查我的输出 txt 文件时，里面什么都没有！我可能做错了什么？输入文件包含 3.1415 2.718 1.414。
#include <iostream>
#include <fstream>
#include <iomanip>
using namespace std;
int main()
{
float fValue;
fstream inputFile;
ofstream outputFile;
inputFile.open("C:\\Users\\David\\Desktop\\inputFile.txt");
outputFile.open("C:\\Users\\David\\Desktop\\outputfile.txt");
cout << fixed << showpoint;
cout << setprecision(3);
cout << "Items in input-file:\t " << "Items in out-put File: " << endl;
inputFile >> fValue; // gets the fiest value from the input
while (inputFile) // single loop that reads(from inputfile) and writes(to outputfile) each number at a time.
{
cout << fValue << …为什么我输出的数组长度为0？它使我的循环不起作用,我对这段代码的理解也不清楚.
<!DOCTYPE html>
<html>
<head>
<title>My Awsome Website</title>
</head>
<body>
<h1>My list</h1>
<ul>
<li>one</li>
<li>two</li>
<li>three</li>
</ul>
<script>
var list = document.getElementsByTagName('<li>');
document.write(list.length);
/*
for (var i = 0; i < list.length; i++) {
list[i].style.backgroundColor = 'red';
list[i].style.color = 'white';
}
*/
</script>
</body>
</html>
没有任何东西出现在浏览器中,因为JavaScript没有编译器来运行它虽然我不知道如何检查这种语言的错误.
我的HTML
<!doctype html>
<html>
<head>
<title>Where am I?></title>
<script src="script4.js"></script>
</head>
<body>
</body>
</html>
我的script4.js
var number = 20;
switch(number) {
case number > 0:
alert(number + " is Positive");
break;
case number === 0:
alert(number + " is zero");
break;
case number < 0;
alert(number + " is negative");
default:
alert(number + " is not a number");
}
我曾尝试阅读有关该主题的其他帖子,但还没有运气.在下面的代码中,为什么f2()不能访问f1()中定义的var.var"name"不是函数f2()的全局吗？不应该f2()看到var"名称"？
function f1() {
var name = "david";
function f2() {
document.writeln(name);
}
document.writeln(name);
}
f2(); // does not write out "david".
我不明白为什么我的新文件中有一堆特殊字符不在原始文件中.这与Learn Python The Hard Way中的 ex17类似.
#How to copy data from one file into another
from sys import argv
from os.path import exists
script, from_file, to_file = argv
print "Copying from %s to %s" % (from_file, to_file)
from_data = open(from_file, "r").read()
print "The input file is %d bytes long" % len(from_data)
print "Checking if output file exist..... %r" % exists(to_file)
print "Hit return to continue or Cntl C to quit"
#keyboard input
raw_input()
out_file = open(to_file, "r+")
out_file.write(from_data)
print …